“We can see that this year, with the black rainstorm, the quality and quantity of the soil did not improve,” he said, referring to a record-breaking deluge in September.

“This has much to do with the trees’ health and whether their roots can develop well enough to hold the trees in place.”

On Wednesday, the Development Bureau revealed that about 4,790 trees had been downed or severely damaged by inclement weather events until late October this year, including typhoons and rainstorms, three times more than the 1,320 recorded in 2022.

The city registered 2,070 fallen or severely damaged trees in 2021, 1,040 in 2020 and 850 in 2019.

In 2018, after Typhoon Mangkhut slammed into the city, authorities removed 31,158 trees rendered unstable.

Of this year’s 4,790 fallen trees, 485 were Bauhinia blakeana, making Hong Kong’s floral emblem the most affected species in 2023. About 421 were Formosa acacia and 316 were sea hibiscus.

So said trees such as the bauhinia species were prone to damage from typhoons because they were brittle and widely planted across the city.

“Other countries have planted a lot of bauhinia and its related species, but they have specified that rigorous and regular pruning is necessary for such trees to maintain their structure,” he said. “We have a lot in Hong Kong as well.

“But how much resources are put into maintaining their structure after they are planted? We are not sure.”

The bureau said authorities had formulated a selection guideline for trees planted along public streets as a reference for government departments to diversify species in urban areas and “promote the use of native plant species”.

A bureau spokesman noted a holistic review, including a scoring system, was being studied to systematically identify roadside trees that might be at potential risk in the long run, with preliminary recommendations expected to be available in 2024.

“In September 2022, the Development Bureau established a task force to review the existing tree management guidelines and related implementation work,” he said. “Ten improvement measures were proposed in early 2023, which are currently being implemented progressively as scheduled.”

The measures included establishing minimum soil volume and planting depth requirements for newly planted trees, applying monitoring technology, such as micro drilling and sonic tomography, and introducing suitability and sustainability assessments for roadside trees.

In April, Secretary for Development Bernadette Linn Hon-ho said the government had planted about 5 million trees and more than 62 million shrubs over the past decade, adding authorities would continue to develop a greener environment and improve the quality of the city’s living environment.

The chief executive of the Conservancy Association said the government should start pruning trees when they were still young and provide them with ample water and growing conditions to ensure their overall well-being.

“Planting trees in the city is a way to help combat climate change, but the trees themselves have to be capable of withstanding climate change too,” he said. “However, we are not very advanced in this regard.”

Lawmaker Ben Chan Han-pan, of the Democratic Alliance for the Betterment and Progress of Hong Kong, suggested that the government should propose a daily tree care guideline aimed at reducing fallen trees.